1. Field of the Invention
The present invention relates to flame retarded vinyl aromatic polymer compositions, and more particularly relates to flame retarded vinyl aromatic polymer compositions containing a drip suppressant.
2. Description of the Related Art
Vinyl aromatic resins such as acrylonitrile-butadiene-styrene graft copolymers have been previously admixed with flame retardant additives and drip suppressants, see Haaf et al., U.S. Pat. No. 4,107,232, issued Aug. 15, 1978, Liu, U.S. Pat. No. 4,639,486, issued Jan. 27, 1987 and Zabrocki et al., U.S. Pat. No. 4,579,906, issued Apr. 1, 1986, all of which are incorporated herein by reference. Flame retardants have included materials such as brominated compounds, and drip suppressants have included such compounds as halogenated polyolefins such as chlorinated polyethylene and polytetrafluoroethylene. Generally compositions containing chlorinated polyethylene have required the presence of a metal stabilizer such as a tin (Sn) compound to thermally stabilize the antidrip compound. These compositions, however, have at times experienced undesirable levels of blooming of the various additives to the surface of the molded articles made therefrom, thereby resulting in substantial reductions in the gloss levels of the molded articles. In other words, utilization of such compositions to make molded parts for printer housings, computer housings or power tool housings can result in poor surface appearance. Drip suppressants have also included polytetrafluoropolymers, but effective levels in thermoplastic compositions have generally been higher than desired possibly due in part to a need for enhanced dispersion.
Accordingly, there is a need for flame retardant vinyl aromatic compositions containing a flame retardant and a drip suppressant and exhibiting low levels of blooming (exhibiting high levels of surface gloss retention) and exhibiting a desired level of flame retardancy with a minimum of drip suppressant.